SquirrelMail -can't send or receive

Installed ISPConfig3 on a CentOS VM using the Perfect Server Guide. Everything is up and running. I created a website and 2 email users. Since this is a test server it is using IP 10.0.0.11 and does not have a registered domain.

I redirected root mail to User1 in /etc/aliases and that is working. Logwatch reports and RKhunter reports are being received by that user in SquirrelMail.

The problem is that User1 and User2 cannot send or receive emails to/from each other. When I try to send an email it takes forever for the action to complete in the SquirrelMail webpage. It's like Squirrelmail cannot find Postfix. I do not see any obvious errors in the logs.